1. Field of the Invention
The invention relates to a connecting rod of a reciprocating internal combustion engine, and more particularly to a bushing-free connecting rod of an internal combustion engine comprising a flexible structure made of hard material.
2. Description of the Related Art
A connecting rod of an internal combustion engine operates to connect a piston to a crankshaft for transmitting the driving force and movement therebetween. A small end of the connecting rod is connected to the piston via a piston pin, and a big end of the connecting rod is connected to a rod journal of the crankshaft, so that the explosion pressure bear by the piston is transmitted to the crankshaft, and the reciprocating motion of the piston induces the rotary motion of the crankshaft. During the above process, alternating loads including compression, stretching, and bending are imposed on the connecting rod. For a floating piston pin, when the connecting rod works, relative motion will occur between the small end of the connecting rod and the piston rod thereby resulting in abrasion on the small end and the piston pin under the action of the alternating load. The abrasion enlarges the gap between the small end and the piston pin, which leads to abnormal sound of the piston pin, damages on the small end and the piston pin, or even hits on the cylinder. In order to weaken the abrasion between the small end and the piston rod, a wear reducing bimetal bushing is pressed in the small end as a sliding bearing. Oil grooves are milled or oil holes are bored on the bimetal bushing and the small end for collecting the spattered lubricant oil for lubrication during the running of the engine.
As the explosion pressure of the commercial vehicle engine increases, the surface pressure imposed on the bushing of the small end becomes larger and larger, and it is much difficult to select the material for the bearing and to develop engines having high explosion pressure, thereby increasing the production cost.
Upon using sliding bearing in prior art, the base for mounting the sliding bearing adopts an intensified rigid structure for the purpose of providing a reliable interference fit when mounting the sliding bearing. It is the same in the reciprocating internal combustion engine that a sliding bushing is pressed in a center hole having a high rigidity, as shown in FIG. 1. The operational reliability of the conventional connecting structure is restricted by the allowable specific pressure of the alloy material of the bearing, the position of the oil groove on the friction surface, fitting process, micro-appearance of the friction surface, and flexure and deformation of the piston pin when bearing a force. In use, as the bushing is often revolved, the oil path is easy to block, and ablation or interlocking occurs on the friction surface of the bushing alloy due to oil shortage. Thus, the dysfunction of the bushing of the small end of the connecting rod is one of the most common dysfunctions in operation of the reciprocating internal combustion engine.